Conventionally, real-image zoom viewfinders that are configured to form a vertically and horizontally inverted real image using an objective lens having a positive refractive power, convert the real image into an erect image using an erecting prism that is formed by a combination of one or more prisms, and enlarge the erect image using an eyepiece lens having a positive refractive power are known. Further, imaging apparatuses equipped with such a real-image zoom viewfinder are also known.
As an example of an objective lens forming such a real-image zoom viewfinder, one substantially includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power and a fourth lens group having a positive refractive power, wherein a prism having a convex lens surface facing the object side is employed as the fourth lens group, is known (see Japanese Unexamined Patent Publication No. 8 (1996)-190130 (hereinafter, Patent Document 1).
As another example of the objective lens forming such a real-image zoom viewfinder, one includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power and a fourth lens group having a negative refractive power, wherein a prism having a convex lens surface facing the object side and a convex lens surface facing the image side is employed as the third lens group, is known (see Japanese Unexamined Patent Publication No. 2003-131292 (hereinafter, Patent Document 2).